Robin and Scott Spivey look at their home, which has been destroyed by the landslide. The ground began slipping in March, and several homes in the Lakeside Heights neighborhood have been swallowed up.

Photo: Michael Macor, The Chronicle

Robin and Scott Spivey look at their home, which has been destroyed...

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The postal service has stopped delivering and picking up mail in the unstable hillside neighborhood.

Photo: Michael Macor, The Chronicle

The postal service has stopped delivering and picking up mail in...

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Robin and Scott Spivey, stand at the front yard of their home on Tuesday May 14, 2013 in Lakeport, Ca., where the ground continues to sink daily in the Lakeside Heights neighborhood. Their neighbor's home at 5396 Lancaster Rd. (left) is also severely damaged from the slide. Lake County officials are searching for the cause of the a hillside collapse where eight homes have been evacuated and ten more are under imminent evacuation.

Photo: Michael Macor, The Chronicle

Robin and Scott Spivey, stand at the front yard of their home on...

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Al Silva moves his belongings out of his rented home on Lancaster Road, where nearby houses continue to slide.

Photo: Michael Macor, The Chronicle

Al Silva moves his belongings out of his rented home on Lancaster...

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The home at 5432 Lancaster Rd., as seen on on Tuesday May 14, 2013, has also suffered major damage in the Lakeside Heights neighborhood of Lakeport, Ca. Lake County officials are searching for the cause of the a hillside collapse where eight homes have been evacuated and ten more are under imminent evacuation.

Photo: Michael Macor, The Chronicle

The home at 5432 Lancaster Rd., as seen on on Tuesday May 14, 2013,...

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Lake County Board of Supervisors Jeff Smith, Denise Rushing and Jim Comstock meeting with homeowners, on Tuesday May 14, 2013 in Lakeport, Ca. to discuss the sinking ground which is swallowing homes in the Lakeside Heights neighborhood. Lake County officials are searching for the cause of the a hillside collapse where eight homes have been evacuated and ten more are under imminent evacuation.

Photo: Michael Macor, The Chronicle

Lake County Board of Supervisors Jeff Smith, Denise Rushing and...

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Robin and Scott Spivey, stand at the front yard of their home on Tuesday May 14, 2013 in Lakeport, Ca., where the ground continues to sink daily in the Lakeside Heights neighborhood. Lake County officials are searching for the cause of the a hillside collapse where eight homes have been evacuated and ten more are under imminent evacuation.

A mysterious landslide in Lake County that swallowed and crushed homes and left others teetering on the brink appears to have been caused, at least in part, by a water line leak, California water resources and geologic inspectors said Wednesday.

An emergency was declared after the earth suddenly opened up in March and began devouring homes in the Lakeside Heights subdivision, which has spectacular views of Clear Lake and Mount Konocti.

"I pinch myself, and it is reality," said Scott Spivey, 47, standing with his wife, Robin, on what used to be their driveway. It is now on the edge of a 13-foot drop where their crumbled house sits, its two-car garage broken and twisted, the cracked foundation exposed.

Fractures began to appear in early March on the downhill side of the subdivision, which was built in the mid-1980s on as much as 12 feet of fill. The situation got worse daily, as the hillside on the southeastern portion of the development sank. The ground eventually dropped between 12 and 14 feet, crushing two homes - including the Spiveys' ranch-style house - and leaving two others hanging over the edge of a precipice.

The slide forced mandatory evacuations of seven of the 29 homes in the unincorporated neighborhood and voluntary evacuations from six others. The rest of the homeowners remain in limbo as the hillside continues to slide, creating new fissures and cracks every day, officials said.

Saturated hillside

Bill Croyle, chief of the flood operations branch of the California Department of Water Resources, said inspectors with his agency and the California Geological Survey concluded that the soil in the slide area was saturated with water.

"You've got an ongoing water issue, probably related to utilities," said Croyle, who plans to submit a draft technical report Thursday to the California Emergency Management Agency and Lake County. "There is more work that needs to be done to flush this thing out, but our observations confirm that there is a water source up there that is causing the problem."

The findings would confirm what several homeowners believe - that undetected leaks in the subdivision's water line flowed downhill, soaked the hillside and caused the slide.

The geological survey report, released Wednesday, said the southeastern portion of the subdivision was built on a topographic bench that indicated previous erosion and may actually have been an old landslide. Pooled water seen on the site and the saturated condition of the soil "are likely contributing to the landslide movement," said the report.

If it was, in fact, a water leak that caused the landslide, liability would presumablyfall on Lake County, which is in charge of the water and wastewater agency. Officials with the cash-strapped county of about 64,000 are at a loss to explain the collapse, but they have so far denied responsibility, offering volcanic or geothermal activity as possible causes.

The county is in fact pocked with small earthquake faults, geysers and extinct volcanoes, including Cobb Mountain, Mount Konocti and Mount St. Helena. The collapse of what geologists call Cow Mountain actually created the hills around the county seat of Lakeport, on the shores of Clear Lake, California's largest natural lake.

Cracked sewer pipe

Kevin Ingram, the senior administrative analyst for the county, said the first indicator that something was going on was in December when utility workers detected a crack in a sewer pipe. It was repaired, and when they checked it again around March 7 or 8, there was another leak, which was also repaired.

The county checked the water system for leaks on March 25, but Ingram said no problems were found. Another inspection on May 9 found two leaks, which were fixed the next day. Ingram said neither leak was large enough to cause a slide. He suggested groundwater could be the culprit.

A geotechnical investigation of the site in 1979 as part of the development plan found groundwater at the site ranging in depth from 4 1/2 to 10 feet underground. The report stated that the soil "undergoes a significant strength loss and becomes weak and compressible when saturated."

"We continue to see new cracks developing" despite the fact that the leaks were fixed, said Ingram, adding that the county has bypassed water and sewer lines in the slide area since the problem started.

"We have heard that there have always been reports of movement and some cracks, but being that as it may, we have never seen anything like this," he said. "We're trying to get to the heart and find out what the actual source of the slide is. At this point we haven't been able to determine that."

Fire suspected

Randall Fitzgerald, 62, a journalist and author who bought his home in Lakeside Heights a year ago, said he believes the problem began on March 6, when the house across the street caught fire. He said the water line that feeds the hydrant could have ruptured if firefighters shut off the hydrant too fast, causing a spike in pressure. Lakeport Fire Chief Ken Wells denied that such a thing occurred.

Fitzgerald nevertheless contends that a lot of the water found during the sewer pipe repairs in March had actually been flowing downhill from the water line.

"How long was this going on?" Fitzgerald asked. "We believe it was flowing for at least 10 days and as long as 60 days."

Questions have also arisen about whether the contractor compacted the soil properly. The state geological report recommends that the county conduct further studies of the water and sewer lines, soil conditions, groundwater levels, geology and other factors that might have contributed to the landslide.

Meanwhile, the Spiveys and the owners of the other red-tagged homes have all been denied coverage by their homeowners insurance carriers. Mail delivery was recently stopped and, for the homes still standing, property values have plummeted from between $200,000 and $280,000 to virtually nothing.

"It gets worse every day," said Spivey, who is renting a home nearby and has stopped paying his mortgage. "Obviously nobody is ever going to live in this place again and it will probably never be rebuilt on this soil."